The invention generally relates to blood collection and processing systems and methods.
Systems composed of multiple, interconnected plastic bags have met widespread use and acceptance in the collection, processing and storage of blood components. Using these systems, whole blood is collected and separated into its clinical components (typically red blood cells, platelets, and plasma). The components are individually stored and used to treat a multiplicity of specific conditions and diseased states.
Before storing blood components for later transfusion, it is believed to be desirable to minimize the presence of impurities or other materials that may cause undesired side effects in the recipient. For example, because of possible reactions, it is generally considered desirable to remove substantially all the leukocytes from blood components before storage, or at least before transfusion.
Filtration is conventionally used to accomplish leuko-reduction. Systems and methods for reducing the number of leukocytes by filtration in multiple blood bag configurations are described, e.g., in Stewart U.S. Pat. No. 4,997,577, Stewart et al. U.S. Pat. No. 5,128,048, Johnson et al. U.S. Pat. No. 5,180,504, and Bellotti et. al. U.S. Pat. No. 5,527,472.
One aspect of the invention provides systems and methods for removing leukocytes from blood using a filter media having a main filter region comprising a porous membrane structure extending between first and second skin surfaces. The porous membrane structure is formed by intersecting cells having a range of diameters. The cells adjacent to the first skin surface have diameters generally smaller than the diameters of the cells adjacent to the second skin surface. The first skin surface includes an open area defined by pores, which are formed by the intersection of cells with the first skin surface. The majority of the open area is defined by pores having a diameter of between about 12 xcexcm and 28 xcexcm.
In one embodiment, the main filter region includes a polyethersulfone material.
In one embodiment, the filter media is enclosed in a housing. The housing comprises first and second flexible sheets made of a meltable material. A peripheral seal joins the sheets directly to the filter media to encapsulate the filter media between the first and second sheets. The seal includes a commingled melted matrix comprising material of the sheets and material of the filter media.
Another aspect of the invention provides systems and methods for removing leukocytes from blood using a filter media having a main filter region. The main filter region comprises a layered porous membrane structure that includes several regions of larger pore sizes alternating in the direction of flow with several regions of smaller pore sizes, or vice versa. Blood traversing the main filter region thereby passes in succession through several alternating regions of smaller, then larger, then smaller diameter pores, or vice versa.